Wiring board interconnection arrangement and display device including same

ABSTRACT

The display device includes a display panel and a plurality of wiring boards placed along the periphery of the display panel. The display panel has panel-side connection wiring for electrically connecting first and second wiring boards adjacent to each other among the plurality of wiring boards. Each of the plurality of wiring boards has an insulating base, a board-side wiring group running on the insulating base, and at least one driving circuit element for driving the display panel. The board-side wiring group is composed of element-connected wiring electrically connected to the driving circuit element and non-connected wiring having no electrical connection to the driving circuit element. The panel-side connection wiring is formed so that the element-connected wiring of the first wiring board and the non-connected wiring of the second wiring board are electrically connected to each other.

This Nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No(s). 2002-269839 and 2003-305592 tiled in JAPANon Sep. 17, 2002 and Aug. 29, 2003, the entire contents of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a display device. The display device ofthe present invention can be a liquid crystal display device, organicand inorganic electroluminescence (EL) display device, a plasma displaydevice and the like, for example.

Conventionally, in liquid crystal display (LCD) devices, a tape carrierpackage (TCP) mode is mainly adopted for mounting of liquid crystal (LC)driving ICs to an LC panel. FIG. 17A is a perspective viewdiagrammatically showing a TCP-mode LCD device. This LCD device, denotedby 500, includes an LC panel 501, and gate TCPs 502, source TCPs 503 andexternal circuit boards 504 placed along the periphery of the LC panel501. The gate TCPs 502 and the source TCPs 503 are respectively providedfor supplying signals to gate signal lines and source signal lines ofthe LC panel 501. The external circuit boards 504 are provided forsupplying external signals to the gate TCPs 502 and the source TCPs 503.

FIG. 17B is a perspective view diagrammatically showing one gate TCP502/source TCP 503. Each of the gate TCPs 502 and the source TCPs 503includes an LC driving IC 505, signal input wiring 507 and signal outputwiring 508 formed on a flexible base 506. The signal input wiring 507supplies external signals, such as image data signals, a power supplyvoltage for IC driving and a power supply voltage for counter electrodedriving, to the LC driving IC 505. The signal output wiring 508 suppliessignals output from the LC driving IC 505.

The signal input wiring 507 of each of the gate TCPs 502 and the sourceTCPs 503 is electrically connected to terminals on the external circuitboard 504, which is a printed wiring board (PWB) placed outside the LCpanel 501, to lead the external signals to the LC driving IC 505 fromthe terminals on the external circuit board 504.

FIG. 18 is a view demonstrating signal input of the TCP-mode LCD device.In the LCD device 500, signals are directly input into the individualsource TCPs 503, for example, from the external circuit board 504.Therefore, a considerably large number of wiring lines must be formed onthe external circuit board 504. To accommodate these wiring lines, somecontrivance such as forming the external circuit board 504 as amultilayer structure is necessary, and this causes disadvantages such ascomplicating the fabrication process, increasing the cost and decreasingthe reliability.

To overcome the problem of the conventional TCP mode described above, a“signal propagation mode” has been introduced, in which a signal is oncesupplied to one TCP and then propagated to the adjacent TCPsequentially. This mode is disclosed in Japanese Laid-Open PatentPublication No. 4-313731, No. 10-214858, No. 2001-056481 and No.2002-287655 and Japanese Laid-Open Utility Model Publication No.3-114820, for example.

The signal propagation mode will be described with reference to FIG. 19.FIG. 19 is a view demonstrating signal input of an LCD device adoptingthe signal propagation mode. Each TCP 601 includes an LC driving IC 602,signal input wiring 603 for supply of an external signal to the LCdriving IC 602, signal output wiring 605 for supply of an image signalfrom the LC driving IC 602 to an LC panel 604, and relay wiring 606 foroutputting an LC driving signal to the adjacent TCP 601.

In the LCD device described above, when an external signal is suppliedto a first-stage LC driving IC 602 a from an external circuit board 607via the signal input wiring 603, an image signal corresponding to thesupplied external signal is sent to the LC panel 604 via the first-stageLC driving IC 602 a and the signal output wiring 605. At this time, partof the external signal input into the first-stage LC driving IC 602 a islead to the relay wiring 606, to be supplied to the signal input wiring603 of the adjacent second-stage TCP 601 b via connection wiring 608running on the LC panel 604.

Therefore, once a signal is input into the first-stage TCP 601 a fromthe external circuit board 607, part of the signal is output to a pixelof the LC panel 604 via the LC driving IC 602 a of the TCP 601 a. Theremainder of the signal is sequentially propagated to the adjacent TCPs601 b, 601 c and 601 d via the relay wiring 606 of the respective TCPs601 and the connection wiring 608 on the LC panel 604.

The LCD device of the signal propagation mode using the relay wiring 606can widely reduce the number of wiring lines required for input ofsignals from the external circuit board 607 into the TCPs 601 a, 601 b,601 c and 601 d. For the external circuit board 607 on which a largenumber of wiring lines must be formed, some contrivance such as givingmultiple layers is made to accommodate the large number of wiring lines.In this situation, the reduction of the number of wiring lines canreduce the number of layers, and this leads to cost reduction of theexternal circuit board 607.

However, the wiring structure in the signal propagation mode disclosedin the above-mentioned publications and the like has the followingproblem. External image signals are input into the LC driving ICs of therespective TCPs via the same wiring line. That is, a composite signalcomposed of image signals for the respective LC driving ICs in thenumber equal to the number of TCPs is input into the same wiring line.This inevitably causes increase of the clock frequency and thusadversely affects electromagnetic interference (EMI). Therefore,adopting this wiring structure will be more difficult as the LCD deviceis higher in definition.

SUMMARY OF THE INVENTION

An object of the present invention is providing a display device capableof suppressing increase of the clock frequency of signals.

The display device of the present invention includes a display panel anda plurality of wiring boards placed along a periphery of the displaypanel, wherein the display panel has panel-side connection wiring forelectrically connecting a first wiring board and a second wiring boardadjacent to each other among the plurality of wiring boards, each of theplurality of wiring boards has an insulating base, a board-side wiringgroup running on the insulating base, and at least one driving circuitelement for driving the display panel, the board-side wiring group iscomposed of element-connected wiring electrically connected to thedriving circuit element and non-connected wiring having no electricalconnection to the driving circuit element, and the panel-side connectionwiring is formed so that the element-connected wiring of the firstwiring board and the non-connected wiring of the second wiring board areelectrically connected to each other.

The plurality of wiring boards preferably have wiring patterns identicalin board-side wiring group.

Preferably, a plurality of lines constituting the board-side wiringgroup run on the insulating base without crossing each other, thenon-connected wiring is in a roughly U shape as viewed from top withboth ends at the periphery of the insulating base, and at least one endof the element-connected wiring is located inside or outside both endsof the non-connected wiring at the periphery of the insulating base, orthe element-connected wiring is interposed between a plurality of linesof the non-connected wiring.

Preferably, the non-connected wiring has another roughly U shape asviewed from top in at least a portion near one end extending in adirection away from the other end.

Preferably, each of the plurality of wiring boards has n or n+1 sets oflines that constitute the board-side wiring group and are involved insignal transmission where n is the total number of driving circuitelements of the plurality of wiring boards (n is a natural number equalto or more than 2). Note that a “line involved in signal transmission”refers to a line through which a signal to be input into or output fromany of the plurality of driving circuit elements of the plurality ofwiring boards is transmitted.

Each wiring board may further have board-side spare wiring electricallyconnected to the driving circuit element, the display panel may furtherhave gate lines, source lines crossing the gate lines, switchingelements electrically connected to the gate lines and the source lines,pixel electrodes connected to the gate lines and the source lines viathe switching elements, and panel-side spare wiring electricallyconnected to the board-side spare wiring, and the panel-side sparewiring may cross the source lines via an insulating film near both endsof the source lines.

The display panel may be a liquid crystal panel.

The wiring board of the present invention has an insulating base, asignal wiring group running on the insulating base for transmittingsignals, and at least one circuit element, wherein the signal wiringgroup is composed of element-connected wiring electrically connected tothe circuit element and non-connected wiring having no electricalconnection to the circuit element.

The wiring board may be placed along a periphery of a display panel, andthe signals may be drive signals for driving the display panel.

Preferably, a plurality of signal lines constituting the signal wiringgroup run on the insulating base without crossing each other, thenon-connected wiring is in a roughly U shape as viewed from top withboth ends at the periphery of the insulating base, and at least one endof the element-connected wiring is located inside or outside both endsof the non-connected wiring at the periphery of the insulating base, orthe element-connected wiring is interposed between a plurality of linesof the non-connected wiring.

Preferably, the non-connected wiring has another roughly U shape asviewed from top in at least a portion near one end extending in adirection away from the other end.

Alternatively, the wiring board of the present invention is the wiringboard provided for the display device of the present invention. Thedisplay panel of the present invention is the display panel provided forthe display device of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic plan view of the entire structure of an LCDdevice.

FIG. 2 is a schematic view illustrating a wiring structure in Embodiment1.

FIG. 3 is a schematic view illustrating a wiring structure in Embodiment2.

FIG. 4 is a schematic view illustrating a wiring structure in Embodiment3.

FIG. 5 is a schematic view illustrating a wiring structure in Embodiment4.

FIG. 6 is a schematic view illustrating a wiring structure in Embodiment5.

FIG. 7 is a schematic view illustrating an alteration to Embodiment 1.

FIG. 8 is a schematic view illustrating an alteration to Embodiment 2.

FIG. 9 is a schematic view illustrating an alteration to Embodiment 3.

FIG. 10 is a schematic view illustrating an alteration to Embodiment 4.

FIG. 11 is a schematic view illustrating an alteration to Embodiment 5.

FIG. 12 is a schematic view diagrammatically illustrating multi-chiptype COFs in which two LC driving ICs are mounted on a COF that issimilar to that shown in FIG. 7.

FIG. 13 is a schematic view diagrammatically illustrating multi-chiptype COFs in which two LC driving ICs are mounted on a COF that issimilar to that shown in FIG. 8.

FIG. 14 is a schematic view illustrating a wiring structure inEmbodiment 8.

FIG. 15 is a schematic view illustrating another wiring structure inEmbodiment 8.

FIG. 16 is a schematic view illustrating an alteration to Embodiment 8.

FIG. 17A is a diagrammatic perspective view of a TCP-mode LCD device.

FIG. 17B is a diagrammatic perspective view of a gate TCP 502/source TCP503.

FIG. 18 is a view demonstrating signal input of a TCP-mode LCD device.

FIG. 19 is a view demonstrating signal input of an LCD device of asignal propagation mode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingembodiments, the present invention is applied to a liquid crystaldisplay (LCD) device. However, the present invention can also be appliedto a plasma display panel (PDP), organic and inorganicelectroluminescence (EL) display devices, an electrochromic displaydevice and the like. The LCD devices shown in the following embodimentscan be any of a transmission type, a reflection type and areflection/transmission type.

First, a rough entire structure of the LCD device will be described withreference to FIG. 1. FIG. 1 is a diagrammatic plan view of the entirestructure of the LCD device. An area within the ellipse in FIG. 1 willbe described in detail in Embodiments 1 to 8.

The LCD device includes a liquid crystal (LC) panel 100, and a pluralityof source chips on film (COFs) 3, a plurality of gate COFs 4 and asignal input flexible printed circuit (FPC) 5 placed along the periphery6 of the LC panel 100. Although three source COFs 3, two gate COFs 4 andone signal input FPC 5 are shown in FIG. 1, the numbers of thesecomponents are not restrictive.

The LC panel 100 includes a thin film transistor (TFT) substrate 1, acolor filter substrate 2 opposed to the TFT substrate 1, and a liquidcrystal layer (not shown) interposed between the substrates 1 and 2. Thethickness of the LC panel 100 is about 0.4 to 0.7 mm.

The TFT substrate 1 includes: a plurality of gate lines running inparallel with each other in a row direction; a plurality of source linesrunning in parallel with each other in a column direction respectivelycrossing the plurality of gate lines; TFTs arranged in a matrix to beelectrically connected to the gate lines and the source lines; and pixelelectrodes connected to the gate lines and the source lines via theTFTs. Terminals for connecting the source COFs 3, the gate COFs 4 andthe signal input FPC 5 to one another are formed on the periphery 6 ofthe TFT substrate 1.

The color filter substrate 2 includes red, green and blue color filtersand a common electrode covering the color filters. Rubbed alignmentfilms are formed on the surfaces of the TFT substrate 1 and the colorfilter substrate 2 facing the liquid crystal layer.

Each of the source COFs 3 and the gate COFs 4 includes: a thin film basemade of glass, polyimide resin or the like having a thickness of 25 to40 μm; and a wiring pattern made of copper foil or the like having athickness of 8 to 12 μm formed on the thin film base. The wiringpattern, composed of a plurality of wiring lines, is formed by platingor casting. A solder resist made of polyimide or the like having athickness of 25 to 50 μm is formed over the wiring pattern excludingportions connected to the periphery 6 of the LC panel 100, to insulatethe wiring pattern. An LC driving IC 8 is mounted on the center portionof each of the source COFs 3 and the gate COFs 4. Openings are formedthrough the solder resist at positions connected to terminals of the LCdriving IC 8, to thereby permit electrical connection between some ofthe plurality of wiring lines constituting the wiring pattern and theterminals of the LC driving IC 8. Various components other than the LCdriving IC 8 may also be mounted on the source COFs 3 and the gate COFs4.

The source COFs 3, the gate COFs 4 and the signal input FPC 5 areconnected to terminals formed on the periphery 6 of the LC panel 100(hereinafter, such terminals are called LC panel terminals) via ananisotropic conductive film (ACF) by thermocompression bonding. The ACFis formed by dispersing thousands to tens of thousands of conductiveparticles, insulating particles and the like in an insulating adhesive.The ACF not only bonds terminals of the source COFs 3, the gate COFs 4and the signal input FPC 5 to the LC panel terminals with the adhesive,but also electrically connects these terminals to each other via theconductive particles. The insulating particles in the ACF serve toprevent adjacent terminals from being short-circuited via linkingconductive particles. The thickness of the ACF is desirably in the rangeof 10 to 50 μm. In particular, about 20 μm or less is preferred. Thewidth of the ACF is preferably in the range of 1 to 3 mm.

As the conductive particles described above, usable are metal particlessuch as Ni particles, metal particles such as Ni particles plated withAu, carbon particles, plated thermoplastic resin particles such asthermoplastic resin particles (plastic particles) plated with Au orNi/Au (Au plated after formation of a Ni layer on a base), transparentconductive particles such as indium tin oxide (ITO) particles,conductive particle composite plastic with metal particles such as Niparticles mixed in polyurethane, and the like. Among others, platedthermoplastic resin particles are particularly preferred as theconductive particles. As the insulating particles described above,thermoplastic resin particles (plastic particles) are mainly used. Thediameter of these conductive particles and insulating particles ispreferably in the range of 2 to 12 μm. The plating thickness ispreferably around 0.1 μm. Anisotropic conductive paste (ACP) may be usedin place of the ACF. However, from the standpoint of easiness ofhandling, a film (ACF) is more desirable.

The connection using the ACF will be described. First, an unhardened ACFis stuck on the periphery 6 of the LC panel 100 so as to cover electrodeterminals formed on the periphery 6. The source COFs 3, the gate COFs 4and the signal input FPC 5 are then mounted on the periphery 6 of the LCpanel 100 so that terminals of the source COFs 3, the gate COFs 4 andthe signal input FPC 5 for connection to the electrode terminals of theLC panel 100 are placed above the electrode terminals of the LC panel100. The ACF region (electrode terminal region) of the LC panel 100 isthen compressed via the source COFs 3, the gate COFs 4 and the signalinput FPC 5 with a heated bonding tool (not shown) at a pressure of 2 to5 Mpa for 10 to 20 seconds, to harden the ACF and thus complete theconnection. The heating temperature of the bonding tool is set at about250 to 350° C. so that the final temperature of the ACF region duringcompression is 170 to 220° C. The width of the bonding tool as thecompressing part is desirably about 1 to 3 mm, which is about the sameas the width of the ACF. The connection on the source and gate sides isdesirably performed at one time. Alternatively, the source COFs 3, thegate COFs 4 and the signal input FPC 5 may be connected one by one.

The transmission route of signals propagating on the LCD device will bedescribed. The solid lines in FIG. 1 represent image signal wiring 22for transmitting image signals such as RGB signals to the respective LCdriving ICs 8, where the arrows indicate the transmitting direction. Theimage signals are supplied from the signal input FPC 5, and aretransmitted via image signal wiring running on the periphery 6 of the LCpanel 100 and image signal wiring running on the source COFs 3 and thegate COFs 4 to be input into the LC driving ICs 8 mounted on the COFs 3and 4. In FIG. 1, only one image signal wiring line 22 is shown forsimplification, and it appears as if image signals to be input into therespective COFs 3 and 4 are transmitted together through one signalline. Actually, however, image signals to be input into the respectiveCOFs 3 and 4 are transmitted via separate lines, as will be describedlater.

The dotted lines in FIG. 1 represent spare wiring 23 for transmittingspare signals to the opposite side of the LC panel 100, where the arrowsindicate the transmitting direction. The spare wiring 23 is wiring usedin such an event that transmission of an image signal output from acertain source COF 3 to an image signal output wiring line 7 indicatedby the two-dot chain line is impeded by disconnection of the wiring line7 at a position marked X in FIG. 1 caused by some reason. Although onlyone image signal output wiring line 7 is shown in FIG. 1, a number ofsuch wiring lines actually extend across the LC panel 100 to theopposite side to lead image signals output from the LC driving ICs 8 ofthe source COFs 3 to the TFTs of the LC panel 100.

One or two spare wiring lines run near both ends of each source COF 3 onthe periphery of the LC panel 100 so as to cross the image signal outputwiring 7 with an insulating film interposed therebetween. The sparewiring is routed along the periphery of the LC panel 100.

Once transmission of an image signal is impeded at the position marked Xmentioned above, the portions of the insulating film at the crossingpoints between the disconnected image signal output wiring line 7 andthe spare wiring 23 (two points on the side of the source COF 3 and theopposite side) are broken by irradiating the portions with laser light,to thereby establish another route of supplying the image signal fromthe opposite side. With this new route, the image signal can be broughtto the position marked X from the opposite side, and thus can repair thefault of the panel. In other words, the image signal output wiring line7 is connected to the spare wiring 23 at both ends thereof, forminganother route of supplying the image signal from the opposite side, inaddition to the route of supplying the image signal from the side of thesource COF 3. The signal propagating through the spare wiring 23 at thisoccasion is herein called a spare signal. Wiring other than the sparewiring 23, such as power supply wiring, is also provided. However,description of such wiring having no direct relation with the presentinvention is omitted here.

Embodiment 1

FIG. 2 is a schematic view illustrating the wiring structure inEmbodiment 1, which covers the area within the ellipse in FIG. 1. The LCdriving ICs 8 of the source COFs 3 are shown as being transparent forclarification of the wiring. Note that for simplification ofdescription, only wiring for transmitting image signals is shown, andillustration of other wiring such as common signal wiring (hereinafter,called COM wiring), power supply/ground (GND) wiring, output wiring fromthe LC driving ICs and spare wiring is omitted. Note also that tocollectively represent components of the same kind, only numerical partof each reference code is occasionally expressed omitting alphabeticalpart thereof. For example, source COFs 3 a, 3 b and 3 c are collectivelyexpressed as the source COFs 3 in some cases.

FIG. 2 shows the source COFs 3, the LC driving ICs 8 mounted on thesource COFs 3, transmission wiring 12 for transmitting image signalssupplied from the signal input FPC 5 (see FIG. 1) to the COFs 3,panel-side transmission wiring 13 for transmitting the image signalsbetween the adjacent source COFs 3, and a COF-side wiring group 10 oneach COF for supplying some of the image signals to the LC driving IC 8and passing the remaining image signals to the adjacent source COF 3.Image signals are input into the LC driving IC 8 at an image signalinput point 9. The transmission wiring 12 and the panel-sidetransmission wiring 13 are connected to the COF-side wiring groups 10via the ACF in a connection region 14. For easy understanding, thepanel-side transmission wiring 13 is shown by the bold lines, while theCOF-side wiring groups 10 are shown by the fine lines.

The wiring structure of the source COFs 3 will be described. To transmitimage signals for the respective source COFs 3 a, 3 b and 3 c viaseparate wiring lines, to be input into their LC driving ICs 8, it isnecessary to form wiring lines of the number corresponding to the numberof LC driving ICs 8 of the source COFs 3 to which the image signals aretransmitted. As four image signals are generally input into each LCdriving IC 8, four image signal lines are required for each LC drivingIC 8. Note that in FIG. 2, the four image signal lines are collectivelyshown by one line as one set. In the illustrated example, in which imagesignals are transmitted to the three source COFs 3 a, 3 b and 3 c, threesets of wiring lines are necessary for each COF. The three sets ofwiring lines run on an insulating base of each COF in a rough U shape asviewed from above without crossing one another. Both ends of the wiringlines of each COF are located at a periphery 31 of the insulating basefor connection with the panel-side transmission wiring 12 and 13 via theACF. Hereinafter, the three sets of wiring lines located inside, in themiddle and outside are respectively referred to as inner (upper) wiring10 a, middle wiring 10 b and outer (lower) wiring 10 c.

One of the three sets of wiring 10 a, 10 b and 10 c must be connected tothe LC driving IC 8 of each source COF. Therefore, arrangement is madeto connect only one set of wiring (one line) to the LC driving IC 8. Inthe source COF 3 a on the left as viewed from FIG. 2, the inner wiring10 a is electrically connected to the LC driving IC 8 at the imagesignal input point 9. Such wiring electrically connected to the LCdriving IC 8 is herein called element-connected wiring. The other twosets of wiring 10 b and 10 c are not electrically connected to the LCdriving IC 8 of the source COF 3 a, but transmit image signals suppliedfrom the transmission wiring 12 to the adjacent source COF 3 b. Suchsets of wiring 10 b and 10 c are herein called non-connected wiring.Note that the arrows in FIG. 2 represent the directions in which theimage signals propagate. The wiring having no arrow do not transmitimage signals.

The wiring structure of the LC panel will be described. In each of thesource COFs 3 a, 3 b and 3 c, the wiring 10 a, which supplies imagesignals to the LC driving IC 8, run inside (upper side). The upper,middle and lower sets of the transmission wiring 12 supply image signalsto be input into the left COF 3 a, the middle COF 3 b and the right COF3 c, and are connected to the inner (upper) wiring 10 a, the middlewiring 10 b and the outer (lower) wiring 10 c, respectively. Imagesignals supplied from the upper transmission wiring 12 are input intothe LC driving IC 8 of the left COF 3 a. Image signals supplied from themiddle and lower transmission wiring 12 are passed to the panel-sidetransmission wiring 13 without being input into the LC driving IC 8 ofthe left COF 3 a.

The panel-side transmission wiring 13 for connecting the left COF 3 aand the middle COF 3 b, which is composed of two sets of wiring linesformed not to cross each other, is routed so that the middle wiring 10 band the lower wiring 10 c of the COF 3 a are respectively connected tothe upper wiring 10 a and the middle wiring 10 b of the COF 3 b. Imagesignals supplied from the upper transmission wiring 13 are input intothe LC driving IC 8 of the middle COF 3 b. Image signals supplied fromthe lower transmission wiring 13 are passed to the next panel-sidetransmission wiring 13 without being input into the LC driving IC 8 ofthe middle COF 3 b.

The panel-side transmission wiring 13 for connecting the middle COF 3 band the right COF 3 c, which is composed of one set of wiring lines, isrouted so that the middle wiring 10 b of the COF 3 b is electricallyconnected to the upper wiring 10 a of the COF 3 c. Image signalssupplied from the transmission wiring 13 are input into the LC drivingIC 8 of the right COF 3 c. The lower wiring 10 c of the middle COF 3 band the middle wiring 10 b and the lower wiring 10 c of the right COF 3c are not connected to the transmission wiring 13.

As described above, in this embodiment, the panel-side transmissionwiring 13 is routed so that the connection between the wiring lines ofthe adjacent source COFs is displaced inward by one set of wiring (byone line). To state specifically, the middle wiring 10 b of the COFs 3 aand 3 b is respectively connected to the upper wiring 1 a of theadjacent COFs 3 b and 3 c displaced inward (rightward) by one set ofwiring. Also, the lower wiring 10 c of the COF 3 a is connected to themiddle wiring 10 b of the adjacent COF 3 b displaced inward (rightward)by one set of wiring. With this arrangement, COFs having the same wiringpattern can be used even in the case of supply of individual imagesignals to the individual COFs. If the panel-side transmission wiring 13connects the wiring lines of the adjacent source COFs without thedisplacement, it is necessary to provide a plurality of COFs having LCdriving ICs different in input point. That is, in this embodiment, COFshaving the same wiring structure can be used for transfer of imagesignals to the LC driving ICs of the respective COFs via separate wiringlines.

In this embodiment, the wiring 10 a (element-connected wiring)electrically connected to the LC driving IC 8 is formed inside thewiring lob and 10 c (non-connected wiring) having no electricalconnection with the LC driving LC 8. Therefore, in the connectionbetween the left COF 3 a and the middle COF 3 b so that the wiring linesare displaced inward by one set of wiring (by one line), the two sets oftransmission wiring 13 are prevented from crossing each other. This cansimplify the structure of the transmission wiring 13, compared withconnection involving crossing of the sets of transmission wiring 13.

The portion of the upper wiring line 10 a downstream the input point 9(right portion with respect to the input point 9 as viewed from FIG. 2),which is not used, may be omitted. The lower wiring 10 c of one sourceCOF 3 may be connected to the lower wiring 10 c of the adjacent COF 3.For example, in place of connecting the lower wiring 10 c of the leftCOF 3 a to the middle wiring lob of the middle COF 3 b in displacement,the lower wiring 10 c of the left COF 3 a may be connected to the lowerwiring 10 c of the middle COF 3 b without displacement. In this case,the connection between the wiring lines of the middle COF 3 b and theright COF 3 c is displaced inward by two sets of wiring (by two lines)via the transmission wiring 13 so that the lower wiring 10 c of themiddle COF 3 b is connected to the upper wiring 10 a of the right COF 3c.

In this embodiment, the signal input FPC 5 is placed on the left of theLC panel 100, and image signals are supplied from the left. In the caseof placing the signal input FPC 5 on the right of the LC panel 100 andsupplying image signals from the right, also, the same COFs as thoseused for the supply of image signals from the left can be used only bychanging the way of displacement of the connection between the wiringlines via the panel-side transmission wiring 13.

In this embodiment, image signals can be input into the LC driving ICs 8of the respective COFs via separate wiring lines. Therefore, increase ofthe clock frequency of image signals input into the LC driving ICs 8,which occurs in the wiring structure of the conventional signalpropagation mode, can be suppressed.

Embodiment 2

FIG. 3 is a schematic view illustrating the wiring structure inEmbodiment 2, which covers the area within the ellipse in FIG. 1. Notethat the LC driving ICs 8 of the source COFs 3 are shown as beingtransparent for clarification of the wiring. Note also that forsimplification of description, only wiring for transmitting a sparesignal and COM wiring are shown in FIG. 3, omitting illustration ofother wiring such as power supply/ground (GND) wiring, output wiringfrom the LC driving ICs and image signal wiring. In FIG. 3 and thesubsequent figures, components of the wiring structure havingsubstantially the same functions as those in Embodiment 1 are denoted bythe same reference numerals, and the description thereof is omitted.

The structure in FIG. 3 includes the source COFs 3, the LC driving ICs 8mounted on the source COFs 3, the panel-side transmission wiring 13 fortransmitting a spare signal between the adjacent source COFs 3, theCOF-side wiring group 10 on each source COF 3 for transmitting a sparesignal to the adjacent source COF 3, a spare signal output point 16 atwhich a spare signal is output from the LC driving IC 8, a spare signalinput point 17 at which a spare signals is input into the LC driving IC8, panel-side spare wiring 18 for collecting a spare signal andtransmitting the spare signal to the opposite side of the LC panel,COF-side spare wiring 19 for connecting the panel-side spare wiring 18and the input point 17, panel-side COM wiring 20 and COF-side COM wiring21. The panel-side spare wiring 18 is routed from the right of the rightsource COF 3 c up to the opposite side of the LC panel.

The source COFs 3 are connected to the LC panel 100 via the ACF in theconnection region 14, to thereby establish connection between thepanel-side transmission wiring 13 and the COF-side wiring groups 10,connection between the panel-side spare wiring 18 and the COF-side sparewiring 19, and connection between the panel-side COM wiring 20 and theCOF-side COM wiring 21. A spare signal input into the LC driving ICs 8at the spare signal input point 17 is output at the spare signal outputpoint 16 via a buffer of the LC driving IC 8. In FIG. 3, for easyunderstanding, the panel-side transmission wiring 13 is shown by thebold dotted lines, while the COF-side wiring groups are shown by thefine dotted lines. As for the COM wiring, the panel-side COM wiring isshown by the bold one-dot chain lines, while the COF-side COM wiring isshown by the fine one-dot chain lines. In FIG. 3, for simplification,normally two (or one in not a few cases) spare wiring lines for each COFare shown by one line as one set. The arrows in FIG. 3 represent thedirections in which a signal propagates. The wiring having no arrow donot transmit the signal.

The wiring structure of the source COFs 3 will be described. In thisembodiment, in which three source COFs are provided, supply of threesets of spare signals is required for one COF. Three sets of wiringlines run on an insulating base of each COF in a rough U shape as viewedfrom above without crossing one another. Both ends of these wiring lineson each COF are located at the periphery 31 of the insulating base forconnection with the panel-side transfer wiring 13 via the ACF.Hereinafter, the three sets of wiring lines located inside, in themiddle and outside are respectively referred to as inner (upper) wiring10 a, middle wiring 10 b and outer (lower) wiring 10 c. The spare signaloutput point 16 is provided for one of these sets of wiring forcollecting a spare signal coming from the panel via the buffer of the LCdriving IC 8. In this embodiment, the output point 16 is provided forthe inner wiring 10 a. The reason why the spare signal is collected viathe buffer of the LC driving IC 8 is to eliminate the necessity ofoverstriding the COF-side COM line 21, which is routed between theCOF-side spare wiring 19 and the inner wiring 10 a, by means of a jumperchip or the like.

The wiring structure of the LC panel will be described. A spare signalis transmitted from left to right as viewed from FIG. 3. Therefore, inthe connection between the adjacent COFs via the panel-side transferline 13, the positions of the sets of wiring connected are displacedoutward (leftward) by one set between the adjacent COFs so that theinner wiring 10 a of the left COF 3 a permitting output of a sparesignal is connected to the middle wiring 10 b of the middle COF 3 bhaving no spare signal output point. Further, to connect the middlewiring 10 b of the middle COF 3 b permitting propagation of the sparesignal to the outer wiring 10 c of the right COF 3 c, the panel-sidetransmission wiring 13 is routed so that the positions of the sets ofwiring connected are displaced outward (leftward) by one set between theadjacent COFs. In this way, spare signals at the respective COFs 3 a, 3b and 3 c are transmitted to the panel-side spare wiring 18 connected tothe right COF 3 c on the right.

As described above, in this embodiment, the panel-side transmissionwiring 13 is routed so that the positions of the sets of wiringconnected are displaced outward by one set between the adjacent sourceCOFs. With this arrangement, COFs having the same wiring pattern can beused as the adjacent source COFs connected to each other. If thepanel-side transmission wiring 13 connects the sets of wiring of theadjacent source COFs without the displacement, that is, if the wiringcounterparts of the adjacent COFs are connected to each other, it willbe necessary to provide a plurality of types of COFs different in sparesignal output point. That is to say, in this embodiment, COFs having thesame wiring structure can be used for transfer of spare signals from theLC driving ICs of the respective COFs via separate wiring lines.

The left portion of the inner wiring 10 a with respect to the sparesignal output point 16 as viewed from FIG. 3, which is not used, may beomitted. In this embodiment, the panel-side transmission wiring 13 isrouted so that the positions of the sets of wiring connected aredisplaced by one set between the adjacent COFs. Alternatively, the innerwiring 10 a of the left COF 3 a may be connected to the outer wiring 10c of the middle COF 3 b by displacement by two sets. In this case, theinner wiring 10 a of the middle COF 3 b is connected to the middlewiring 10 b of the right COF 3 c by displacement by one set, while theouter wiring 10 c of the middle COF 3 b is connected to the outer wiring10 c of the right COF 3 c without displacement.

In this embodiment, the spare signals were transmitted from left toright of the LC panel 100. In the case of transmitting the spare signalsfrom right to left, also, the same COFs as those used for thetransmission from left to right can be used only by changing the way ofdisplacement with the panel-side transmission wiring 13.

Embodiment 3

FIG. 4 is a schematic view illustrating the wiring structure inEmbodiment 3, which covers the area within the ellipse in FIG. 1. Thisembodiment is an application of Embodiment 1. In Embodiment 1, thesignal input FPC 5 is located either on the left or right side, to allowsupply of image signals from only one side. In this embodiment, thesignal input FPC 5 is located on each of the left and right sides, toallow supply of image signals in two parts from the left and right sidesfor one COF.

The source COF 3 in this embodiment is different from the source COF 3in Embodiment 1 in that an additional set of wiring 10 d having theimage signal input point 9 is formed outside the wiring 10 c. Inaddition, the LC panel 100 in this embodiment has transmission wiring 12extending from the right-side signal input FPC (not shown). The numberof wiring lines for each set is two in this case because the normallyfour image signals are divided into two.

The wiring structure of each source COF 3 will be described. In thisembodiment, the COF-side wiring unused in Embodiment 1 is effectivelyused. First, the three sets of wiring 10 a, 10 b and 10 c are routed asin Embodiment 1 on the source COFs 3 a, 3 b and 3 c. In addition,another set of wiring 10 d having the image signal input point 9 isrouted outside the wiring 10 c. Note that one set is composed of twowiring lines in this embodiment.

The connection between the transmission wiring 12 extending from theright-side signal input FPC and the right source COF 3 c is made so thatimage signals for the right COF, the middle COF and the left COF aresupplied to the sets of wiring 10 d, 10 c and 10 b of the right COF 3 c,respectively. Using the wiring 10 d, as well as the sets of wiring 10 a,10 b and 10 c, the panel-side transmission wiring 13 is routed toconnect the sets of wiring of the adjacent COFs in displacement asdescribed in Embodiment 1. In this embodiment, in which the wiring 10 dhaving the image signal input point 9 runs outermost, the panel-sidetransmission wiring 13 is routed so that the positions of the sets ofwiring connected are displaced outward by one set between the adjacentCOFs.

Specifically, the panel-side transmission wiring 13 for connecting theright COF 3 c and the middle COF 3 b is routed so that the wiring 10 bof the COF 3 c is electrically connected to the wiring 10 c of the COF 3b and the wiring 10 c of the COF 3 c is electrically connected to thewiring 10 d of the COF 3 b. Likewise, the panel-side transmission wiring13 for connecting the middle COF 3 b and the left COF 3 a is routed sothat the wiring 10 c of the COF 3 b is electrically connected to thewiring 10 d of the COF 3 a.

With the wiring structure described above, image signals can be suppliedin two parts from the left and right sides simultaneously. In addition,since effective use of the three sets of wiring 10 a, 10 b and 10 c ispossible unlike Embodiment 1, the number of wiring lines for each COFcan be reduced. Specifically, a total of 12 wiring lines (6 sets×2lines) will be necessary for each COF to transmit image signals to beinput into the respective COFs via separate wiring lines. In thisembodiment, however, only 8 wiring lines (4 sets×2 lines) are enough.

Embodiment 4

FIG. 5 is a schematic view illustrating the wiring structure inEmbodiment 4, which covers the area within the ellipse in FIG. 1. Thisembodiment is an application of Embodiment 2. In Embodiment 2, sparesignals are transmitted either leftward or rightward. In thisembodiment, spare signals are transmitted in two parts both leftward andrightward.

The source COF 3 in this embodiment is different from the source COF 3in Embodiment 2 in that an additional set of wiring 10 d having thespare signal output point 16 is formed outside the wiring 10 c, tothereby enable transmission of a spare signal from right to left inaddition to the transmission in the opposite direction. The number ofwiring lines for each set is one in this case because normally two sparesignals are divided into two.

The wiring structure of each source COF 3 will be described. In thisembodiment, the wiring unused in Embodiment 2 is effectively used.First, three sets of wiring 10 a, 10 b and 10 c are routed as inEmbodiment 2 on the source COFs 3 a, 3 b and 3 c. In addition, anotherset of wiring 10 d having the spare signal output point 16 is routedoutside the wiring 10 c. Note that one set is composed of one wiringline in this embodiment. In this embodiment, there are provided twospare signal output points 16 for collecting a spare signal coming fromthe panel via the buffer of the LC driving IC 8. This enablestransmission of the spare signal in both left and right directions.

The connection between the spare wiring 18 and the transmission wiring13 on the panel and the source COFs 3 a, 3 b and 3 c is as described inEmbodiment 2. In this embodiment, in which the wiring 10 d having thespare signal output point 16 is located outermost, the panel-sidetransmission wiring 13 is routed so that the positions of the sets ofwiring connected are displaced inward by one set between the adjacentCOFs. Specifically, the panel-side transmission wiring 13 for connectingthe right COF 3 c and the middle COF 3 b is routed so that the wiring 10d of the COF 3 c is electrically connected to the wiring 10 c of the COF3 b. Likewise, the panel-side transmission wiring 13 for connecting themiddle COF 3 b and the left COF 3 a is routed so that the wiring 10 cand the wiring 10 d of the COF 3 b are electrically connected to thewiring 10 b and the wiring 10 c of the COF 3 a, respectively.

With the wiring structure described above, a spare signal can besupplied in two parts to both the left and right ends. In addition,since effective use of the three sets of wiring 10 a, 10 b and 10 c ispossible unlike Embodiment 2, the number of wiring lines for each COFcan be reduced. Specifically, although a total of 6 wiring lines aregenerally necessary, only 4 wiring lines are enough in this embodiment.

Embodiment 5

FIG. 6 is a schematic view illustrating the wiring structure inEmbodiment 5, which covers the area within the ellipse in FIG. 1. Thewiring structures were described separately for image signals inEmbodiment 1 and for spare signals in Embodiment 2. In this embodiment,a wiring structure combining these two wiring structures will bedescribed.

The source COF 3 in this embodiment is different from the source COF 3in Embodiment 2 in that an additional set of wiring 10 d having theimage signal input point 9 is formed outside the wiring 10 c, to therebyenable transmission of image signals from left to right as in Embodiment1 and transmission of spare signals from left to right as in Embodiment2.

The wiring structure of each source COF 3 will be described. In thisembodiment, the wiring lines unused in Embodiment 2 are effectivelyused. First, three sets of wiring 10 a, 10 b and 10 c are routed as inEmbodiment 2 on the source COFs 3 a, 3 b and 3 c. In addition, anotherset of wiring 10 d having the image signal input point 9 is routedoutside the wiring 10 c. In this embodiment, one set is composed of twowiring lines for the wiring 10 a, while it is composed of four wiringlines for the remaining sets of wiring 10 b, 10 c and 10 d.

The connection between the spare wiring 18 and the transmission wiring13 on the panel and the source COFs 3 a, 3 b and 3 c is substantiallythe same as that in Embodiment 2. However, with the wiring 10 d havingthe image signal input point 9 located outermost, the displacement ofthe connection between the sets of wiring of the adjacent COFs isopposite to the case of Embodiment 1 in which the wiring having theimage signal input point 9 is located innermost. Specifically, thepanel-side transmission wiring 13 for connecting the left COF 3 a andthe middle COF 3 b is routed so that the wiring 10 b and the wiring 10 cof the COF 3 a are electrically connected to the wiring 10 c and thewiring 10 d of the COF 3 b. Also, the panel-side transmission wiring 13for connecting the middle COF 3 b and the right COF 3 c is routed sothat the wiring 10 c of the COF 3 b is electrically connected to thewiring 10 d of the COF 3 c.

In this embodiment, COFs having the same wiring structure can be usedfor transfer of image signals into and transfer of spare signals fromthe LC driving ICs of the respective COFs via separate lines. With thewiring structure in this embodiment, the number of COF-side wiring linescan be reduced from the number obtained by simply adding the numbers ofCOF-side wiring lines in Embodiments 1 and 2. Specifically, the simplyadded number of wiring lines is 18, where the number of wiring lines inEmbodiment 1 is 12 (3 sets×4 lines) and that in Embodiment 2 is 6 (3sets×2 lines). In this embodiment, the number can be reduced to 14 (1set×2 lines+3 sets×4 lines).

Embodiment 6

A plurality of embodiments are conceivable by combining and applyingEmbodiments 1 to 5. Some of such embodiments will be described withreference to FIGS. 7 to 11. FIGS. 7 to 11 show alterations toEmbodiments 1 to 5 and correspond to FIGS. 2 to 6, respectively.

Each source COF 3 described in Embodiments 1 to 5 has an unused wiringportion, which is specifically a wiring portion left after the input ofan image signal at the image signal input point 9 or a wiring portionexisting before the output of a spare signal at the spare signal outputpoint 16. In FIGS. 7 to 11, such unnecessary wiring portions areeliminated from the wiring structures in Embodiments 1 to 5.

As shown in FIGS. 7 to 11, with the elimination of the unnecessarywiring portions, the sets of wiring 10 b and 10 c are displaced towardthe eliminated wiring by one set on the COF. For example, in each sourceCOF 3 shown in FIG. 7, while the wiring 10 b is the second from theinnermost on the left with respect to the LC driving IC 8, it isdisplaced inward by one set to the innermost on the right. By adoptingthe wiring structures shown in FIGS. 7 to 11, the number of COF-sidewiring lines can be reduced.

Embodiment 7

In Embodiments 1 to 6, one LC driving IC 8 is mounted on one COF. Thepresent invention is also applicable to a multi-chip type COF on which aplurality of LC driving ICs are mounted.

FIGS. 12 and 13 are schematic views diagrammatically illustratingmulti-chip type COFs having two LC driving ICs mounted on one COF. Thewiring structures shown in FIGS. 12 and 13 are applications of thewiring structures shown in FIGS. 7 and 8, respectively.

Each of the left and right COFs 3 a and 3 b shown in FIG. 12 includestwo LC driving ICs 5 aa and 8 ab (5 ba and 8 bb) mounted on aninsulating thin film base and four sets of wiring 10 a, 10 b, 10 c and10 d. The first wiring 10 a, which is the innermost one among the foursets of wiring 10 a to 10 d, is electrically connected to the left LCdriving IC 8 aa (8 ba) at an image signal input point 9 a. The secondwiring 10 b, which is the second innermost one, extends under the leftLC driving IC 8 aa (8 ba) and is electrically connected to the right LCdriving IC 8 ab (8 bb) at an image signal input point 9 b. The remainingthird and fourth wiring 10 c and 10 d extend in a roughly U shape asviewed from top with both ends at the periphery of the insulating base.That is to say, two sets of wiring 10 a and 10 b among the four sets ofwiring 10 a, 10 b, 10 c and 10 d are element-connected wiring, while theremaining sets of wiring 10 c and 10 d are non-connected wiring.

The wiring structure on the panel will be described. Four sets oftransmission wiring 12 a, 12 b, 12 c and 12 d are connected to the firstwiring 10 a, the second wiring 10 b, the third wiring 10 c and thefourth wiring 10 d, respectively, for transmission of image signals tobe input into the left and right LC driving ICs 8 aa and 8 ab of theleft COF 3 a and the left and right LC driving ICs 8 ba and 8 bb of theright COF 3 b, respectively. The image signal supplied from the firsttransmission wiring 12 a is input into the left LC driving IC 8 aa, andthe image signal supplied from the second transmission wiring 12 b isinput into the right LC driving IC 8 ab. The image signals supplied fromthe other sets of transmission wiring 12 c and 12 d are not input intothe LC driving ICs of the left COF 3 a but are passed to the panel-sidetransmission wiring 13.

The panel-side transmission wiring 13 for connecting the left COF 3 aand the right COF 3 b is routed so that the third wiring 10 c and thefourth wiring 10 d of the left COF 3 a are electrically connected to thefirst wiring 10 a and the second wiring 10 b of the right COF 3 b,respectively. This panel-side transmission wiring 13 is composed of twosets of wiring arranged not to cross each other. The image signalsupplied from the upper set of transmission wiring 13 is input into theleft LC driving IC 8 ba, while the image signal supplied from the lowerset of transmission wiring 13 is input into the right LC driving IC 8bb.

Next, the multi-chip type COFs shown in FIG. 13 will be described. Eachof the left and right source COFs 3 a and 3 b shown in FIG. 13 includestwo LC driving ICs 8 aa and 8 ab (8 ba and 8 bb) mounted on aninsulating thin film base and four sets of wiring 10 a, 10 b, 10 c and10 d. The first wiring 10 a, which is the innermost one among the foursets of wiring 10 a to 10 d, is electrically connected to the right LCdriving IC 8 ab (8 bb) at a spare signal output point 16 b. The secondwiring 10 b, which is the second innermost one, extends under the rightLC driving IC 8 ab (8 bb) and is connected to the left LC driving IC 8aa (8 ba) at a spare signal output point 16 a. The remaining sets ofthird and fourth wiring 10 c and 10 d extend in a roughly U shape asviewed from top with both ends at the periphery of the insulating base.That is to say, two sets of wiring 10 a and 10 b among the four sets ofwiring 10 a, 10 b, 10 c and 10 d are element-connected wiring, while theremaining two sets of wiring 10 c and 10 d are non-connected wiring.

Each of the source COFs 3 a and 3 b has spare signal input points 17 aand 17 b for inputting a spare signal into the two LC driving ICs 8 aaand 8 ab (8 ba and 8 bb), COF-side spare wiring 19 a and 19 b forconnecting panel-side spare wiring 18 a and 18 b and the input points 17a and 17 b, and the COF-side COM wiring 21 connected to the panel-sideCOM wiring 20.

The wiring structure on the LC panel will be described. For transfer ofa spare signal from the left source COF 3 a to the right source COF 3 b,these COFs are connected via panel-side transmission wiring 13 a and 13b. Specifically, the two sets of transmission wiring 13 a and 13 b arerouted on the panel so that the first wiring 10 a and the second wiring10 b of the left COF 3 a permitting output of a spare signal areconnected to the third wiring 10 c and the fourth wiring 10 d of theright COF 3 b having no spare signal output point.

In this embodiment, as in Embodiments 1 and 2, the LC driving ICs 8 aa,8 ab, 8 ba and 8 bb having the same structure and the source COFs 3 aand 3 b having the same structure can be used for input of individualexternal signals (spare signals) into the LC driving ICs (or outputthereof from the LC driving ICs) via separate wiring lines. In addition,in this embodiment, in which each of the COFs 3 a and 3 b has two LCdriving ICs 8 aa and 8 ab (8 ba and 8 bb), the number of lines of thepanel-side transmission wiring 13 for connecting the COFs 3 a and 3 bcan be reduced. In general, the panel-side wiring is high in resistancebecause the wiring thickness is small compared with that of the COF-sidewiring. Therefore, if the number of lines of panel-side wiring is large,the connection resistance will become very high, and this degradessignals supplied to the LC driving ICs. As a result, the LC driving ICsmay fail to operate normally. In this embodiment, in which the number oflines of the panel-side wiring 13 can be reduced, the wiring resistancecan be made smaller than those in Embodiment 1 and 2. Therefore, signalssupplied from the signal input FPC 5 can be more suppressed fromdegrading, and the number of LC driving ICs 8 drivable by one FPC 5 canbe increased.

In FIGS. 12 and 13, two LC driving ICs were mounted on each of the COFs3 a and 3 b. Alternatively, three or more LC driving ICs may be mountedon each COF.

Embodiment 8

In all the source COFs 3 in Embodiments 1 to 7, the connection terminalsof the COF-side wiring groups 10 are placed on one periphery (upperperiphery as viewed from the figure) of the thin film base (insulatingbase). To connect such terminals of the adjacent source COFs 3, thetransmission wiring 13 is routed in a roughly U shape as viewed fromtop. The source COFs 3 in this embodiment has wiring groups 10 routed ina roughly Z shape as viewed from top, so that the connection terminalsof the adjacent source COFs 3 face each other.

FIGS. 14 and 15 are schematic views illustrating wiring structures inthis embodiment. This embodiment is an alteration to Embodiment 1 shownin FIG. 2. In each of the source COFs 3 a, 3 b and 3 c shown in FIGS. 14and 15, a portion of the wiring group 10 near one terminal is routed ina roughly U shape as viewed from top. In the illustrated examples, theleft portion of the wiring group 10 with respect to the IC driving IC 8is routed in a roughly U shape. That is to say, each of the source COF 3a, 3 b and 3 c has the wiring group 10 in a roughly Z shape.

The source COFs 3 a, 3 b and 3 c are electrically connected to oneanother via the panel-side transmission wiring 13, as in Embodiment 1.The wiring groups 10 of the adjacent source COFs are connected indisplacement by one set of wiring by displacing one source COF in FIG.14 and by displacing the panel-side transmission wiring 13 in FIG. 15.Specifically, the middle wiring 10 b and the lower wiring 10 c of theleft source COF 3 a are electrically connected to the upper wiring 10 aand the middle wiring 10 b of the middle source COF 3 b, respectively.The middle wiring 10 b of the middle source COF 3 b is electricallyconnected to the upper wiring 10 a of the right source COF 3 c.

FIG. 16 is a schematic view illustrating an alteration to thisembodiment. In the source COFs 3 a, 3 b and 3 c shown in FIGS. 14 and15, only the portion of the wiring group 10 near one terminal is routedin a roughly U shape. In FIG. 16, the portions of the wiring group 10near both terminals are routed in a roughly U shape in the left andright source COFs 3 a and 3 c. The middle source COF 3 b interposedbetween the left and right source COFs 3 a and 3 c has the same wiringstructure as the source COFs 3 shown in FIG. 2, having no roughly Ushaped portion in the connection region 14. The middle source COF 3 bhas only two sets of wiring, the upper wiring 10 a and the lower wiring10 b. The middle wiring 10 b and the lower wiring 10 c of the leftsource COF 3 a are electrically connected to the upper wiring 10 a andthe lower wiring 10 b of the middle source COF 3 b, respectively, andthe lower wiring 10 b of the middle source COF 3 b is electricallyconnected to the upper wiring 10 a of the right source COF 3 c.

In this embodiment and its alteration, the distance between theconnection terminals of the adjacent source COFs 3 a and 3 b, forexample, can be shortened. In other words, short panel-side transmissionwiring 13 can be used to electrically connect the adjacent COFs 3. Asdescribed in Embodiment 7, in general, the panel-side wiring is high inresistance because the wiring thickness is small compared with that ofthe COF-side wiring. Therefore, use of a long-routed panel-sidetransmission wiring 13 for electrical connection between the adjacentCOFs 3 will increase the resistance value between the adjacent COFs 3.This degrades signals supplied from the signal input FPC 5 to the LCdriving ICs 8, and as a result, the LC driving ICs may fail to operatenormally. In this embodiment, in which the panel-side transmissionwiring 13 can be shortened, the wiring resistance can be made smallerthan those in Embodiments 1 to 7. Therefore, signals supplied from thesignal input FPC 5 can be more suppressed from degrading, and the numberof LC driving ICs 8 drivable by one FPC 5 can be increased.

The portion of the upper wiring 10 a downstream the image signal inputpoint 9 (right portion with respect to the input point 9), which is notused, may be omitted. In this embodiment, in each of the source COFs 3a, 3 b and 3 c, the left portion of the wiring group is 10 with respectto the LC driving IC 8 was routed in a roughly U shape. Alternatively,the right portion of the wiring group 10 may be routed in a roughly Ushape.

Other embodiments

In Embodiments 1 to 8, the source COFs 3 were described. The gate COFs 4may have a similar wiring structure. The COFs were used as the wiringboards in Embodiments 1 to 8. Alternatively, chips on glass (COGs) andTCPs may be used as the wiring boards. The COFs may be connected to thedisplay panel by face-up bonding or face-down bonding.

In Embodiments 1 to 8, at least one end of the element-connected wiringis located inside or outside both ends of the non-connected wiring. Inother words, the innermost (or outermost) wiring is theelement-connected wiring. Alternatively, the element-connected wiringmay be interposed between a plurality of sets of non-connected wiring.In other words, the element-connected wiring may not necessarily beplaced innermost or outermost.

In Embodiments 1 to 8, TFTs were used as the switching elements.Alternatively, two-terminal elements such as metal insulator metal (MIM)elements and other three-terminal elements may be used. In Embodiments 1to 8, the display panel was active-matrix driven. The present inventioncan also be applied to passive-matrix driven display panels.

The display device of the present invention can be a liquid crystaldisplay device, organic and inorganic EL display devices, a plasmadisplay device and the like. The wiring board of the present inventioncan be COF, COG, TCP and the like.

According to the display device of the present invention, signals to beinput into driving circuit elements or signals output from drivingcircuit elements are allowed to propagate through separate wiring lines.This can suppress increase of the clock frequency of signals.

While the present invention has been described in preferred embodiments,it will be apparent to those skilled in the art that the disclosedinvention may be modified in numerous ways and may assume manyembodiments other than that specifically set out and described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention which fall within the true spirit andscope of the invention.

1. A display device comprising a display panel and a plurality of wiringboards placed along a periphery of the display panel, wherein thedisplay panel has panel-side connection wiring for electricallyconnecting a first wiring board and a second wiring board adjacent toeach other among the plurality of wiring boards, each of the pluralityof wiring boards has an insulating base, a board-side wiring grouprunning on the insulating base, and at least one driving circuit elementfor driving the display panel, the board-side wiring group is composedof element-connected wiring electrically connected to the drivingcircuit element, first non-connected wiring having no electricalconnection to the driving circuit element and second non-connectedwiring having no electrical connection to the driving circuit element,and the panel-side connection wiring is formed so that theelement-connected wiring of the first wiring board and the firstnon-connected wiring of the second wiring board are electricallyconnected to each other and so that the first non-connecting wiring ofthe first wiring board is connected to the second non-connecting wiringof the second wiring board and so that the element-connected wiring ofthe second wiring board is not electrically connected to the board-sidewiring group of the first wiring board, wherein the plurality of wiringboards have wiring patterns identical in board-side wiring group.
 2. Thedisplay device of claim 1, wherein a plurality of lines constituting theboard-side wiring group run on the insulating base without crossing eachother, the non-connected wiring is in a roughly U shape as viewed fromtop with both ends at the periphery of the insulating base, and at leastone end of the element-connected wiring is located inside or outsideboth ends of the non-connected wiring at the periphery of the insulatingbase, or the element-connected wiring is interposed between a pluralityof lines of the non-connected wiring.
 3. The display device of claim 2,wherein the non-connected wiring has another roughly U shape as viewedfrom top in at least a portion near one end extending in a directionaway from the other end.
 4. The display device of claim 1, wherein eachof the plurality of wiring boards has n or n+1 sets of lines thatconstitute the board-side wiring group and are involved in signaltransmission where n is the total number of driving circuit elements ofthe plurality of wiring boards (n is a natural number equal to or morethan 2).
 5. The display device of claim 1, wherein each wiring boardfurther has board-side spare wiring electrically connected to thedriving circuit element, the display panel further has gate lines,source lines crossing the gate lines, switching elements electricallyconnected to the gate lines and the source lines, pixel electrodesconnected to the gate lines and the source lines via the switchingelements, and panel-side spare wiring electrically connected to theboard-side spare wiring, and the panel-side spare wiring crosses thesource lines via an insulating film near both ends of the source lines.6. The display device of claim 1, wherein the display panel is a liquidcrystal panel.
 7. The wiring board provided for the display device ofclaim
 1. 8. The display panel provided for the display device of claim2.
 9. A display device comprising: a display panel having panel sideconnection wiring; a first wiring board having an insulating base, adriving circuit element for driving the display panel, a first wiringpath connected to the driving circuit element, a second wiring path anda third wiring path; and a second wiring board identical to the firstwiring board and having a first wiring path identical to the firstwiring path of the first wiring board connected to the driving circuitelement, a second wiring path identical to the second wiring path of thefirst wiring board, and a third wiring path identical to the thirdwiring path of the first wiring board; wherein the panel-side connectionwiring connects the second wiring path of the first wiring board to thefirst wiring path of the second wiring board and connects the thirdwiring path of the first wiring board to the second wiring path of thesecond wiring board.
 10. The display device of claim 9, wherein in thepanel-side connection wiring, none of the first, second and third wiringpaths of the second board are connected to the first wiring path of thefirst board.